Switch contact



y 1927 A. RAWLING swI'rcH CONTACT Filed Nov. 5, 192:5

Masses:

- ATToRNev y Patented May 3, 1927.

ARTHUR RAWLING, OF WILKINS-BURG, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELECTRIC & MANUFACTURTNG COMPANY, -A CORPORATION OF PENNSYL- VANIA.

SWITCH CONTACT.

Application sied November 5, 1923. .semi no. evasos.

My invention relates to kswitch mechanism and particularly to ycontact mechanism used in circuit breakers of the truck panel type wherein the circuit breaker is carried by a truck enclosed within a cell or housing` and which makesy contact with fixed contact members when the truck is moved into ope-1 ative positionwithin the cell. i l In a patent application of` H. K. Arising,

Serial No. 592,767, filed October 6, 1922' (Case No. 10,099) and assignedto the lll/vestinghouseElectric 8: Manufacturing Company, switch Contact members are disclosed lwherein `an insulating bushing supports a Contact jaw member in such .manner that the jaw- Ymember is centered with respect to a liXed contact blade memberwhen the contactjaw member is moved into `engagement with the blade member The` contact jaw member comprises apairofcopper straps, eachwof which is provided with an inwardly directed ree'ntrant' contact portion "which yielclingly,` engages the flat surface of the blade member which isembraced'by the contact portions on opposite sides.

i It has been found'that this form of con tact jaw member isvvery e'ective in securing good conductive ycontact between the Jaw members and tlieblade' member. However, it has been found that contact jaw members of this character are overstrained at the bends in` the copperstraps and particularly when the straps are heated by overload currents. The heating reduces the elasticity lof they straps and reduces the contact pressure thereof. y

It is an object of my l a contact jaw member ofthe character described with yielding reinforcing members suchas steel springs for relieving the copper straps of the burden of maintaining close contact with the blade member, thereby increasingthe life of the contact jawmeinbers' considerably. i l A y l Another object of my invention is to provide Contact tensioningmeans that may be readily, applied to standard constructions of `the above vspecified type and `which rmay I y readily be replaced in the event that they havebeen weakened by severe service. 'It' will be seen that thev tensioning springs are considerably cheaper thanthe copper straps and the cost of repair is materially reduced.

invention to provide Another object ofviny inventionis to pro'- Q vide. a tensioning device for contact jaw members having. the above-described characteristics that is inexpensive to` manufacture o of my invention are attained by means of the i switch contact members hereindescribed and p y' illustrated in the accompanyingy drawings," wherein Figure 1 is anelevational view ofthe'y improved contact device, and

. Fg. Q'is a plan view of the copperstraps constituting the switch jaws of the contact device. o

Refer-ring to the drawings, the device comaXial Abore extendingv therethough and which is providedwith a metal bracket 5 by means of which the bushing is attached to a frame structure 6- thatV constitutes apart of the truck uponwh'ich the circuitvbreaker embodying the contact'device is carried. K

The inner end.Y of the bushing '3 is provided witha metal clamping device that securelyV retains al pair .of copper switch yprises an insulating bushingV 3 havingfanqv jaw straps 8 and 9. The straps are spaced y l lapart Aby means of a spacing member 10 and the clamp member and .the straps 8 and 9 are drawn tightly togethervby means of' a bolt 11. The inner lends of thestraps 8 and 9 are `connected to a terminal device'of the circuit breaker (not shown). by means of a clamp bolt 12. l

The' outer eiid ofthe bushing is provided witlia metalvwasher -ldliaving threaded' openings for receiving clamping bolts 14 that extend longitudinally through the bushing and which serve to attach the vclamp member .7 thereto. The washer 13 is provided with an opening 2O through which the outer end `of the contact lstraps 8 and 9 extends, theopening being` of such size as to'permit of` limited lateral displacement of the 'iieizible contact straps 8 and 9. By

1 reasonl of the'latferal displacement of the con-` tact straps, the contact jawy members, which constitute integral parts'of the straps, may

be centered with respect to contact blade.

member 15 that is mounted upon an insulat-A v10o y ing bushing 16 that is secured tot a frame y structure 17 which constitutes a partof the cell in' which the circuit enclosed. i

The outer ends of the contact straps S and 9 terminate in contactjaw members 1S and. 19respectively. The jaw members combrealer truck is prise oit-set portions which constitutes the main portions or the contact jaw members and reentrant contact portions 21 and 22, that yieldingly engage the blade member and embrace it between them. The contact jaw' members 18 and 19 are normally biased toward one another and their separating movenient limited by means ot'a bolt 23 that extei'idsthrough openings in the jaw members.

` Vhen the contactjaw member is movedv toward lthe blade member '15, the end of which' slightlyY sharpened, the contact portions 21` and are separated against ten-` sion thereof and yieldingly embrace the blade member. In order to reinforce'` the contact jaw members 18 and 19, and to relieve the strain of the n'iaterial at the bends 24, I provide steel leaf springs and 26 that engage opposite sides of the contact menjibers '18 and 19 and. which yielding-ly press the contact portions 21 and 22 into engagement with the blade member 15.

The spring member 25 comprises a flat steel leaf of Ufshape that is clamped Abetween the insulatingbushing 3 and the washer 13. The ends of the leall spring 25 are beaded at 27 for the purpose ot providing a rounded contact surface which reduces the itrictional wear to a minimum. The leaf vsprings 26 are o U-shape and are inserted between the portions 18 and. 21, and 19 and 22, of lthe contact jaw members and are normally -compresed therebetween. The spring 25 is preferably of greater' strength than the springs 26 inorder to opposethe expansive effect oit the springs 26, and, consequently, kthe tull tension of the outer spring 25 is transmitted to the Contact portions `21 and 22 through the medium of the spr-ings 26. The

vsteel springs'are relatively7 `wide andvhave an etxensiveheat radiating surface and engage the contact aw members with a line contact and consequently any tendency of the contact straps to heat the steel 'springs is reduced to a minimum.

By reason olf this construction, contactV )aw members ot standard construction and a predetermined size may be used for conducting larger currents than has heretofore been 'practiced because the copper straps maybe operated at higher temperatures lwithout reno. ducting the tensionot the contact portions u upon the blade member. Soft copperstraps may be used in place of the former hardened straps if desirable.

It will be seen that the steel springs may be applied to contact jaw members of standard construction Without necessitating any alteration thereof and thatthe bolt 23,that serves to limit the separating movement the contact jaw members, also serves'to re- Yof the heat which atfected the elasticity thereof. When this occurred it wasnecessary to remove the contacty straps and replace them with tempered straps. This operation necessitatedl disconnecting the straps from the circuit breaker and removal ot the bushing from the circuit-breaker truck entailin 1 a considerable loss of time and material. order to replace the steel springs, it is only necessary to take down the outerend assembly from the bushing 'and replace new springs which are relatively inexpensive compared to ,y the cost of copper Contact straps. I

While I ment of my invention it will be apparent to those skilled in the art thatv various modifications, changes, substitutions, additions and omissions may be made in the apparatus illustrated without departing tromI the spirit and scope of my invention, as set orth in vthe appended claims.

I claim as my invention: A. contact Jaw member comprising a 'sup- `port member, a pair of Contact jaw members `movably mounted upon the support member and having a reentrant contact p0rtion overlapping the main portion for engaging and receiving a switch blade member therebetween, means for limiting separation of the jaw members and spring membersy disposed betweeny the said'contact portion vand main portion of the Jaw members and retained in operative position vby the said ymeans for yieldingly pressing thecontact portions into engagement with the said switch blade member.v

In testimony whereof', I yhave hereunto subscribed my name this 29th day of Ocaber, i923.

- y' ARTHUR YRAWLrNe.

have illustrated but one embodi- 

